When a well is to be abandoned, the wellhead is normally cut from the supporting tubular string and used on other wells. Since the wellhead is a very expensive item, great care has to be taken to avoid damaging it in the cutting and removal process. It is also desirable in some cases to make the casing cut as close to the wellhead as possible.
One example of how this was done in the past is illustrated in U.S. Pat. No. 5,318,115. The equipment illustrated there is a combination of a support and a motor driving a rotary tubing cutter with extendable blades. The support is an elaborate grapple design that features pivoting members that hook over the top of the wellhead and land in an external wellhead groove to brace the apparatus against reaction forces when the cutter is actuated. An alternative support of a threaded engagement into the top of the wellhead is suggested. The problem with this design is that it is complex and expensive and the wellhead has to be configured to accept the external grapple hook-shaped members that have to be pivoted into position. The wellhead is prepared with this feature which is used for the wellhead connector. The gripping members have to a have a depth of grip that matches the external groove locations on the wellhead. If the wellhead has no such grab locations, or if they are not in a specific location, the tool becomes useless in recovery of the wellhead. The threaded connection to a subsea wellhead entails risk of damage to the wellhead at the threads or further internally.
The present invention provides solutions to this problem that protect the wellhead and allow a common tool to be employed on a variety of wellhead designs that don't need to be specially made to accept the tool. The gripping assembly is simply actuated below the wellhead after passing through it and using a support shoulder to land near the bottom of the wellhead. As an alternative, the support shoulder can land on top of the wellhead to properly space out the grip assembly to land on an internal wellhead surface while minimizing damage from such grip or where a grip mark will not affect the operation of the wellhead. Those skilled in the art will further appreciate the various aspects of the invention from a review of the preferred embodiment and its associated drawings that appear below while recognizing that the claims define the full scope of the invention.